1. Field of the Invention
The present invention relates to a compressor and an oil amount management system for a compressor.
2. Description of the Related Art
Gifford-McMahon (GM) refrigerators, pulse tube refrigerators, Stirling refrigerators, and Solvay refrigerators are capable of cooling a target object to a temperature ranging from about 100 K (Kelvin) (low temperature) to 4 K (extremely low temperature). Such refrigerators are used to cool a superconducting magnet or a detector or used in cryopumps, etc. The refrigerator is provided with a compressor for compressing helium gas used as an operating gas in the refrigerator.
In some compressors, oil is used to cool heat generated by compressing an operating gas or to lubricate the compressor. In these compressors, presence of an appropriate amount of oil is essential for proper operation. For this reason, these compressors need periodical maintenance.
There is proposed a technology of detecting the level of the oil surface (oil level) in the oil separator in the compressor and estimating the amount of oil in the compressor in order to detect shortage of oil in the compressor.